add test for topping and update code to pass it
add Gemfile with ruby 2.0.0 and pry activated
add failing test to check whether added topping is vegetarian
add vegetarian argument to topping's initialize method
add initialize method with toppings argument as an array to Pizza class
add test to initialize instance of Pizza class with toppings array
add failing test for checking default value of toppings array
fix initialize method to instantiate Pizza class with default topping of cheese